Electron discharge device



Filed Feb. 12, 1946 2 Sheets-Sheet l IN VEN TOR. 11'. H. BurneTT H15ATTORNEY.

'2 Sheets-Sheet 2 Leg 5OVOLT5 e iOOVOLTS ,eq =15 OVOLTO C) O -a J- H.BURNETT 6q KOOVOL-TS 8 (D ANODE VOLTS ELECTRON DISCHARGE DEVICE oowANODE CURRENT-VOLTAGE CHARACTERISTICS Feb. 27, 1951 Filed Feb. 12, 1946FIG. 4.

A-8p 200 vows 4 42 100 VOLTS ZOO INVENTOR. J. H. B urneTT 8p 50 vowsH115 ATTORNEY ANODE CURRENT- CONTROL ELECTRODE CHARACTERISTICS CONTROLELEMENT VOLTS M50150 Lo IozH mum OMKMQZ SJHZ PZMEIDU MDOZ Patented Feb.27, 1951 ELECTRON DISCHARGE DEVICE James H2 Burnett, Upper Montclair, N.J., as-

sianor,,,by mesneassignments, to, General-Rail: way Signal, Company, a,corporation; of New York 1.

Application February 12, 1946; Serial No; 64?;007

3 Claims. (01. 2505-5215.)

This invention relates to electronicdevices; and more particular-1vtoucontrollable;electron discharge devices suitable: for amplifiersoscillators, and the. like.

In the usual type of controllable electron discharge tubes, such asexemplified bythe ordinary and well known triode, electrons are.attracted: to the grid: whenever it assumes a positive potential withrespect to the. cathode and the, resultant grid current: imposeslimitations upon the efiicient and effective usexof" such tubes-invarious. applications. In power amplifiersand. oscillators, for example,the grid current flowing duringthe; time thegrid is DOSltlVGJSBPIBSBIItSa. substantial part: ofthe electron space current: and; is; aiwaste-qful'power loss. In voltage amplifiers and similar applications of theconventional triodeu where: it is desired to have thegoutput vary withinclose limits with the variations; ofitheinput; voltage. impressed onthegrid, the fiowof' grid; current: when the grid assumes a positivepotential tends to modify the potential on thegrid; and-cause distortionof the-output. Al'soyi-n various; applica tions of the usualtriode, thegri'dgcurrentexisting while the. grid. is positive 118151.21. tendencytooverheat the grid; and cause. undesirable; thermionic or secondaryemission of electronsfrom the rid-, particularly where thoriatedjtungsten or oxide coated cathodesare usedin the interests: of emissionefiiciency and the grid may accumulate: a depositof emissivermaterialevaporated or sputteredfrom the'cathode. "These and other limis tati'onsin the efficiency and, use of the usual; type of grid controlled.electrondischarge tube, are due primarilyto the: attraction of electronsto the grid when it assumes positive potential withrespect to. thecathode;- andthese, limitations can be'mitigated and in manyrespects-entirely. over-: come and the efficiency and utility of suchtubes clearly'increased;if the flDWriQf eleotronsrto th positive gridcan Ice-effectively prevented.

With these considerations in mind, one of the objects of thepresentminvention is to; provide a' controllable electron discharge:device--which maybe proportioned to 'havesthe desirableopera atingcharacteristics of; the: usual: grid :control; triode or similarmultiple electrode tubes, but which does not have, any appreciableelectron current to the grid-or control electroda; evenwhen this grid orcontrol-1 electrodeassumes rela-- tively high positive,potentialsxwithrespectpto the; cathode;

A further object of: the; invention is tov attain this desirable objective by' a" simpler-and effective structural organization, in whichtheloomponent parts may be readily proportioned and arranged to. obtainanydesired rating and operating characteristiQS.

Various other-objects, attributes and characteristic features-ofthe'invention will be in part apparent, and in part pointed out, as thenature of the inventionand certain specific embodiments are hereinafterdescribed.

Generally-speaking, and without attemptingto define the natureand scopeof the invention, it is proposed to combine a: magnetic field with acathode, anode, and'a control electrode in such a, Way that, althoughthe control electrode may perform its usual functionofcontrolling theelectron space current in accordance with variations inits-impressedpotential, the electrons emitted by the cathode andformingthe electron or space current; are; influenced, by the magneticfield, so asnot to reach the control electrode or grid, even thoughit.assumes a, relatively high positive potentialwith respect to thecathodein the operation of the tubes Considering thegeneral attributes of theinvention from another viewpoint, the control element-or electrode,instead of being the conventional grid with'spaces between its wiresfor, the passage of electrons and located'between the cathode and anodein the path of direct movement of electrons from thecathode to theanode, is. disposed to one side of the direct or normal path ofelectrons emitted by the cathode and attracted to the anode, butin sucha position that variations in the electrostatic field due to potentialson the control electrode may influence the intensity of theelectron-current and exercise the same controlling function as the gridof the conventional' triode; and thisarr-angement or disposition ofcathode, anode and control electrode is supplemented by a magnetic fieldacting in a direction and with-such intensity as to confine the movementof electrons emitted from the cathode-into, a beam or stream over adischarge pathof the appropriatearea which does not touch the controlelectrode; even though it assumes a.

relatively high positive potential with respect to ent, in explainingthe nature and attributes of the invention, to refer to the specificembodiments of the invention illustrated in the accompanying drawings ina schematic and diagrammatic manner, the parts being shown in thesedrawings more with a view of facilitating an explanationand'understanding of the invention than for the purpose of illustratingthe details of any particular construction and arrangement of parts thatmay be advantageously employed in practice.

In the accompanying drawings,

Fig. 1 is a general view, partly in section and partly in perspective,of one elemental form of controllable electron discharge tube embodyingthe invention;

Fig. 2 is a diagrammatic representation of the relationship and functionof the component elements of the tube of Fig. 1, with a schematicrepresentation of associated circuit connections;

Fig. 3 illustrates diagrammatically a variation in the disposition ofthe elements of the tube of Fig. 1 in connection with a magnetic fieldprovided by a permanent magnet; and

Figs. 4 and 5 illustrate, for explanatory purposes, typical curves ofthe operating characteristics of one form of tube embodying theinvention.

Considering first the structural organization of what may be said to bean elemental form of an electron discharge tube of this invention asshown in Fig. 1, this tube comprises a thermionic emissive cathode C ofthe filamentary type, which may be a directly heated wire of tungsten orother emissive metal, a wire thoriated or oxide coated, or a cathode ofthe oxide coated indirectly heated type, the particular type of thecathode not being material to the present invention.

The cathode shown is assumed to be a nickel core wire spirally woundwith a fine nickel wire to aid adherence of the emissive coating and tohelp in maintaining a uniform temperature.

In the interests of efficiency of low operating temperature, it isconsidered preferable for ordinary applications to employ an oxidecoated cathode formed and treated in the manner disclosed in the priorpatents to D. V. Edwards, et al., No. 1,985,855, December 25,1934, andNo. 2,- 081,864, May 25, 1937, because it is found that such a cathodehas superior qualities in the way of life and durability, as well ashigh emissivity at relatively low temperatures.

In the simplified arrangement illustrated, this cathode C is welded orotherwise suitably attached at its ends to non-emissive supports 5, 6sealed in the reentrant stem or press I of the glass envelope E for thetube, said supports 5, 6 being connected by leads in the usual way topins 8, 9 of a base I0 cemented to the glass envelope in accordance withthe usual practice.

In the elemental type of tube shown in Fig. 1, the anode comprises twolike flat plates A, A located on oppositesides of the cathode C inplanes substantially parallel to the linear axis of the cathode, withthe edges of said plates parallel with the cathode at substantiallyequal distances from the cathode. As shown in Fig. 1, these anode platesA, A are located parallel with each other above and below the cathode Cat equal distances in conformity with the desired voltage and currentcharacteristics of the tube.

In the simplified construction illustrated, the two anode plates A and Aare electrically connected and held in the-proper relative positions bya support or brace H welded to these plates,

4 and the upper anode plate A is supported by a rigid support I2extending through a seal l3 in the upper end of the envelope E andconnected to a terminal cap M in accordance with the usual practice.These anode plates A, A are preferably formed from sheet stock of theappropriate thickness for stiifn'ess or rigidity, with stiffeningflanges or ribs (not shown) if desired, of tantalum, or a likenon-magnetic material capable f 'ofoperating at a high temperature withlow emissivityv and having characteristics suitable for the plates ofelectron discharge tubes.

In the elemental tube shown in Fig. 1, the control electrode, having thefunction of the grid in the conventional 'triode, comprises two likefiat plates G, G located parallel to each other on opposite sides of thecathode C substantially parallel with the cathode and in planessubstantially parallel with the straight line between the anode platesA, A through the. cathode, which may be considered to be .the axis ofthe tube.

As shown, these control electrodes G, G which may conveniently be termedgrids, are assumed to be in the form of fiat sheets of tantalum, or alike non-magnetic material, without any grid wires or openingscharacteristic of the usual grid structure employed in electrondischarge tubes, although it should be understood that these controlelectrodes may be plates with openings therein, or some form of areticulate or striated structure, although such openings are notnecessary for the passage of electrons as in the conventional grid.

In the simplified structure illustrated in Fig. 1, the controlelectrodes or grids G, G are electrically connected and supported in thedesired relationship by a cross support or brace l5 welded thereto; andthis brace is welded to a support l6 sealed in the reentrant stem 1 ofthe envelope E and connected to a pin I! on the base H) in accordancewith the usual practice.

In addition to the electrodes in an evacuated envelope as described,'theelectron discharge tube of this invention further includes suitablemeans for providing a steady magnetic field of the appropriate strengthdirected in a proper direction with respect to the electrodes toinfluence the movement of the electrons in a way to prevent themreaching the control electrodes. In the simplified form of the"elemental tube shown in Fig. 1, this magnetic field is assumed to beprovided by a coil or solenoid M energized with unidirectional current,as indicated by the arrows and symbols and This magnetostatic field isdirected along the axis of the tube substantially at right angles to thesurfaces of the anode plates A, A and parallel to the surfaces of thecontrol electrodes G, G as indicated by the arrow I-I, so that themagnetic lines of force act along the straight and normaljpath formovement of electrons from the cathode C to the anodes A, A

Fig. 3 illustrates schematically a modified organization in which thefilamentary cathode C is disposed vertically in the tube envelope E,shown broken away and partially in section, with the anode plates A, Adisposed vertically on opposite sides of the-cathode. and the controlelectrode plates G, G disposed vertically on opposite sides of thecathode in planes substantially at right angles to the planes of theanodes. In this form of the invention, the steady magnetic field isillustrated as provided by a permanent magnet PM of any one of thewell-known permanent magnet materials, preferably analloy of a manaciron; nickel :andaluminumwommonly fES .Alnico: This-permanentzmagnet PMis positioned asrindicated: diagrammatically .inf'Fig'QaB to pro- 'vide:magnetic: lines. :of :iorce the? rdirfidtiDI'IlIldicatedt by: the arrowTH substantial'ly'at right angles irto the. planes of: the." anodes :A,:A and parallel :tothesurfaces :of the :control electrodesThisipermanent magnet PM is preferably provided-:1 withcsoftciron pole;pieces it to give a :more I effective flux d'istributi-on.

Sincethe total anodercurrent .:.dependsupon the area of r the anode-surfac e-,"- aswell :as the cathode to .anodedistance:andtheaeifectiveanode voltage; it is contemplatedthat.the effective area of the anodemay be increased to obtain desired 'currentwreadings by -elongation;=-ofthe anode plates A,-'A .in Fig-sail. andi3, 1i-n.-a direction par allel.-to [the filament axis. which have their. .-.-width determined-by thespacingof the-control electrodes. G,-.'G .-selected tor the desiredcontrol characteristics. -.Also;--i.t is contemplated that a pluralityof elemental tubeunits, such. as .shown in-Eigs.-l and-3 may=beassembledin the-same envelope and. have their-anodesan-d rcon-trol electrodesinterconnected, or employaanodes anclcontrol electrodes .common toadjacent units-, by any suitable disposition-tor relationship otthepar-ts adaptable .for effectual-mountingand. support of the electrodes:inthe. tube envelope Various arrangements. of .expanding. thesurtace.area of the electrodes of the elemental tube. -unit, .or packingaplurality of tube. elements in some cellularelike organization the sameenvelope may be employed withoutdeparting. iromethe fundamental.attributes -andadvaLn-tages of .this

invention.

The particular organizations. illustrated. in Fi s. 1 nd-3 re m lytypical otthe various other geometrical arrangements and disposition ofthe cathode, anode vland control electrode, to-

gether with means. providinga magnetic field characteristic of thisinvention; and it is contemplated, that these organizations illustratedmay be. modified. and adapted in other ways, in

additionto varying the space relation and dimen- -4 evacuatedof all airand gases; in accordance 65 with recognized practice to provide what isknown as a hard tube;

Consideringnow the function and operation of the controllable .electrondischarge tube of this invention, it is foundthata disposition ofelectrodes, together with a magnetic "field, such'as illustrated anddescribed; provides a control of theelectron-or 'spacecurrent to theanodes in accordance with the variations in "the "potential of thecontrol electrodes with 'respeot'to the cathode, and that thereisnoappreciable movement of electrons to the control electrodes and aresultant'electron current, even though the control electrodes assume arelatively high'positive potential with respect to the cathode; 'reticalconsideration indicates that this action or performance of the device ofthis invention may be attiibuted to certain recognized phenomena inconnection with I the emission and magnetic fields; butit should beunderstood that therollowing; discussionxof a theory-of operation is notcomprehensive, nor necessarily. applicable in all. details to thevarious forms which the tube of this invention may take.-

With regard to the controlling effect of the potentialon thecontrol-electrodes, it may be said that the numberof electrons emittedfrom the. cathode and attractedto the anodes in an electron dischargetube is dependent upon the potential gradient to the cathode, andprimarily the electrostatic field adjacent the cathode. In the tubeofthis. invention, the electrostatic field of the existing potential. onthe control electrodes acts to modify this potential. gradient providedby the space charge and anode voltage in such a Way as to control theelectron current'actually flowing to the anodes and through the externaloutput circuit. It may beassumed that the control electrodes of the tubeof this invention act inz-this respect much like the grid of theconventional triode, -.negative potentials tending to reduce and cut oifelectron current to the anodes, and positive potentials acting toneutralize. the effect of the spacecharge and also supplement the anodepotentials tending to draw electrons from the cathode. In. thisconnection, the relative spacing of the elements as well as the voltagesinvolved, are factors in determining the intensity of the anode currentand the efiectiveness and-range of control of thepotentials on thecontrol electrodes.

Speakinggenerally, it is contemplated for-ordinary uses of the. tubethatthe. cathode willbe capableof emitting a surplus of .electronsat themaximum anodeoperating voltage, so that the anodecurrent is limited byspace charge etlects. Under such conditions, the. anode. current for agiven anode voltage increases .with a decrease in anode.to cathodespacing; and in general the anode to cathodespacing may be choserrforcertain anode voltages to provide the. desired anode current.

With respect to the dimensions and space relation of the controlelectrodes, the effective area of the control electrodes and theirdistance from the. cathode depending in g n al pon th o trol potentialsto-be usedfor the control electrodes, amplification factor, and controlcharacteristics desired, since it may be considered that the controlexercised bythe grid is dependent in general upon the potential or" theelectrostatic field created adjacent the cathode emitting surface by thecombined action of the potentials on the control electrodes G,.G and onthe anode plates A, A When the control electrodes G, G are spaced closerto thecathode C than the anodes A, A as shown in Fig. 2, in generalthere is an increase in the ratio of the effectiveness of the controlelectrode and. anode voltages in producing an electrostatic field .nearthe cathode; and while such relative spacing is generally favorable formany applicationswhere a range of controtvolt'a'geslower'th'an the anodevoltage are desirable, it should be'understo'od that other relativespacings "of the :control electrodes and the anode plates withtrespectto the cathode may be employed without I departing from the invention.Similarly; the'contro'lelectrodes G indicated in Fig.2 as extending mostof the distance be-- tween-theano'de 'platesA and A may extend overanydesired part of thisdist'anc'e, dependent upon the controlcharacteristics desired; or even project beyond the-anodeplates'ifdesired for movement-ofelectrons in dischargetubesandin 75"s't'ructural"purposes; 'In "short; the dimensions and relationship of the tubeelements indicated in the accompanying drawings are merely typical andmay be materially changed without departing from the functions and modeof operation characterizing this invention.

Investigations indicate that the operating characteristics of the tubesof this invention are dependent upon the proportioning and spacing ofthe tube elements in much the same way as in erally speaking, thecathode and anode spacing determines the space charge effect, and theproximity of the control electrodes to the cathode, as well as theirarea and potential as compared with the anodes, determines theeffectiveness of variations in potentials onthe control electrode uponthe flow of anode current. Theoretical considerations, as well asinvestigations, indicate that various parts may be proportioned andspaced and a tube geometry selected to obtain a wide variety ofoperating characteristics.

Considering now the important feature of this invention of utilizing themagnetic field in a way 'to minimize or eleminate electron current tothe control electrodes at positive potentials, it is a familiarphenomena that a magnetic field will influence the path of movement ofan electron.

More specifically, an electron as a negatively charged particle whilemoving in a magnetic field is acted upon by a force which isperpendicular to the direction of movement of the electron as of a giveninstant and also perpendicular to the direction of the magneticfield.This force is dependent upon the strength of the magnetic field, andalso upon the component of the instantaneous velocity of the electronwhich is perpendicular to the direction of the magnetic lines of force.In this respect an electron in motion in a magnetic field may be said tobe subjected to forces similar to those acting on a current carryingconductor moving in a magnetic field; and the same quantitativerelations apply. While an electric field, such as produced by voltageson electrodes in the tube, exerts a force on an electron whether at restor in motion, and in the direction of the field, a magnetic field exertsforce on an electron only when it is in motion, and in a direction atright angles to the direction of such magnetic field. Consequently, amagnetic field does not accelerate or retard the motion of an electronunder the influence of an electric field, but merely changes itsdirection of movement.

Referring to the diagrammatic illustration in Fig. 2, and assuming themagnetic field acts either up or down in the direction indicated by thearrow H along the axis of the tube extending through the cathode andparallel with an imaginary line indicated by the dash lines IE, it canbe seen that electrons leaving the surface of the cathode with aninitial velocity eithe up or down towards an anode plate A or A and inthe same direction as the magnetic lines of force, are not effected bythe magnetic field and move in straight lines toward such anode underthe infiuence of the electric field of the anode voltage. In the case ofelectrons leaving the surface of the cathode with a component ofvelocity at right angles to the magnetic lines of force, however, suchelectrons will be deflected by the magnetic field in accordance withwell known principles; and since these electrons are subject to theinfiuence of the electric field as well as the magnetic field, they willmove in what may be called a spiral path toward one of the anodes. Inother words, it may be said that the magnetic field acts to converge orfocus the electrons leaving the cathode into a beam or stream directedtoward each of the anodes, as indicated by the dotted lines in Fig. 2.

Generally speaking, the path of movement of the electrons emitted fromthe cathode is dependent upon their velocity and the intensity of themagnetic lines of force; and the tube elements may be arranged andproportioned, and anode voltages and magnetic field strength chosen orselected, such that the forces acting on the electrons to confine theminto a prescribed beam, as compared with the forces exerted on theelectrons by positive potentials on control electrodes, will cause allor substantially all of the electrons emitted from the cathode to befocused into a discharge path to the anodes and escape the controlelectrodes. In other words, the strength of the magnetic lines of force,in connection with the proportioning and spacing of the electrodes andvoltages employed, may be such that there is no appreciable electroncurrent to the control electrode, even though said control electrodeassumes a high positive potential with respect to the cathode.

Since the tube of this invention involves the influence of a magneticfield upon the electrons moving from the cathode to the anode, it isdesirable to avoid any weakening or distortion of this magnetic field byemploying non-magnetic metals for the electrodes and many of thesupporting elements. For ordinary purposes it is considered preferableto employ tant lum for the electrodes, on account of the facility withwhich this metal gives up occluded gases and its tendency to absorbgases given off during operation. Molybdenum, or other non-magneticmetals of similar characteristics, are preferably employed for themounting and supporting elements of the tube, except at the glass seals,rather than nickel, commonly employed for such purpose, in order thatthe magnetic qualities of nickel may not adversely affect the magneticflux distribution.

To illustrate this characteristic of the tube of this invention, ascompared with the conven tional triode, Fig. 4 shows curves of anodecurrent plotted against anode voltage for different control elementpotentials per unit of cathode length for a typical tube of thisinvention; and Fig. 5 illustrates similar curves of anode currentagainst control element potential for different anode voltages ofanother typical tube. It should be understood that these curves aremerely representative of one specific form of a tube, but they serve toillustrate how this invention provides a tube in which the control maybe provided by positive control element potentials without anyappreciable or readily measurable electron current to the controlelectrode.

Referring to curves of Fig. 4 for the particular tube underconsideration, it will be noted that there is no appreciable anodecurrent for a zero potential on thescontrol electrode. untilzthe anodehas a voltage of some 5.00- V'ol-ts and thattheincrease inanod'ecurrent-for increaseslin anode voltage is very slight.

As indicated by the curves of Fig. 5, this particular organization givesan electron discharge tube controlled in effect primarily by positivepotentialsof' the control electrode thereby showing a marked contrastwith i the I conventional triode. In this connection, it-- should beunderstood that for the conditions of voltage and cur-- rent shown Figs.4 and 5 there isnoreadily measurable electron current to the controlelectrode; i e

The characteristic curves of Figs. 4 and 5 are merelytypicalor=representative of one specific organization of. the invention,and it should be understood that the dimensions and spacing of theelectrodes may be varied and chosen to-give quite different operatingcharacteristics.

From this illustration and explanation of specific embodiments of theinvention, it can be seen that a magnetic field may be combined with adisposition of electrodes,- constituting a thermionic cathode, anodeanda control electrode, and included in anevacuated envelope, in such a waythat the anode current-may be effectively controlled in accordance withpotentials on the control' electrode, without having any substantial orobjectionable electron current to the control electrode when it assumespositive potentials with respect to the cathode. A controllable electrondischarge tube of this type, characterized by the absence of anyelectron current to the control electrode when positive, may beadvantageously employed in various applications, where the conventionaltriode or similar multiple electrode tube is used, more particularly inpoweramplifiers and oscillators, where the grid current existing withpositive grid potentials and characteristic of the ordinary triode, is alimitation upon efiiciency and performance. Aside from indicatingschematically in Fig. 2 typical connections for input and outputcircuits for the tube of this invention, no attempt has been made toillustrate the circuits for applying a tube of this invention to thefield of amplifiers and oscillators, since the tube of this invention isapplicable to any one of the various types of circuit organizations,commonly used with triodes for such purposes. In short, a tube of thisinvention, which may be termed a magna-triode, is in effect an improvedor equivalent form of the well known conventional triode, and in generalis applicable to all the uses to which such triodes are now applied.

In the particular embodiments of the invention illustrated anddescribed, a filamentary type of cathode has been assumed, and sincesuch a cathode provides electron emission in all directions from itsaxis, it is considered expedient to provide anodes on opposite sides ofsuch cathode, and. similarly two control electrodes. It should beunderstood, however, that this is merely a typical or illustrativeorganization, and that the same principles and mode of operationcharacterizing the invention may be applied to other forms of cathodes,number and arrangement of electrodes. Similarly, while the anodes havebeen illustrated as flat plates, it should be understood that theseanodes may have curved surfaces, as may be best adapted to the operatingcharacteristics of the tube desired.

The current for energizing the coils shown in Figs. Land" zi -forproviding-ether magneticfield characteristic of this invention maybe 1derived from any suitable: source;.and' on. account of the. powerrequirements for such an electroemagnetic field, it isdesirabletousapermanentmagnets to.provideuthis,magnetic field when the,.current.and voltage ratings of the..tube,. or other: operating characteristics,.permitipermanent magnets: to. be-used effectively. within the:spacelimitations desired. L The. term magnet isnusedlforfcomvenienceintheclaims; as a generic expression: to include a-ipermanentmagnet, a.solenoid, or any other type of .like device whichvconstitutes. a source, of magneto-motive-forceh .Various adaptations,modifications, andradditions may be made to the specific embodiments of.the invention. illustrated and described .without departing fromitsunderlying principles, functions,:and mode of operation; and Idesire, to have itunderstood that theinvention isnotjimited to. thespecific structural. organizationsilluse trated or described, but maytake atwid'e: variety of other forms.

What I claim is:

1. A controllable electron. dischargev tubecomprising, an evacuatedenvelope, a straightfilamentary thermionicv :emissive cathode11.11.58.161 envelope, supporting. elements sealed in said envelope forsupportingsaid cathode atiits .ends' and supplying heating currentthereto, an anode within said envelope having opposing surfaces ofsubstantial area on opposite sides of said cathode substantiallyparallel with its axis, said anode surfaces being interconnected withinsaid envelope to operate at the same potential, 3, pair of flat controlelectrodes in said envelope connected together within said envelope anddisposed one on each side of said cathode in planes substantially atright angles to said anode surfaces, elements sealed in said envelopefor providing separate lead-in connections for said anode and controlelectrodes, said anode and control electrodes being of a readilydegassed but nonmagnetic material, and a magnet outside of said envelopeproviding magnetic lines of force directed substantially at right anglesto the axis of said cathode and the surfaces of said anode, said magnetproviding a magnetic field strong enough to prevent significant electroncurrent flow to said control electrodes when the positive potentialsapplied thereto are relatively high and have a substantial effect uponthe electrostatic field at the emissive surface of the cathode and thespace current drawn from said cathode.

2. A controllable electron discharge tube comprising a highly evacuatedenvelope, 2. straight filamentary thermionic emissive cathode supportedat its ends by a pair of supporting elements sealed in one end of saidenvelope, an anode of sheet metal within the envelope having opposingsurfaces on opposite sides of said cathode generally parallel with itsaxis and equidistant therefrom, a rigid connection Within said envelopebetween said anode surfaces to maintain them in their space relationshipand at the same operating potential, a connection for said anode sealedin the other end of said envelope, a control electrode having surfaceson opposite sides of said cathode substantially at right angles to saidanode surfaces, a supporting element for said control electrode sealedin the same end of said envelope as said cathode supporting elements,said anode and control electrodes being of a non-magnetic material, anda magnet outside of said envelope providing a strong magnetic fielddirected transversely of said cathode and substantially at right anglesto said anode surfaces, said magnetic field acting to direct electronsemitted from said cathode under the combined influence of positivepotentials on said control electrode and anode along paths escaping thesurface of said control electrode in spite of a relatively high positivepotential applied thereto, said'magnetic field cooperating with saidcontrol electrode to provide beams of space current extending to saidanode surfaces of an intensity dependent primarily upon the positivepotential of said control electrode and without having significantelectron current flow to said control electrode.

3. A controllable electron discharge tubecomprising a linear thermionicemissive cathode, an anode comprising surfaces extending throughout thelength of said cathode on opposite sides thereof in planes substantiallyparallel with the axis of said cathode, a rigid metallic connectionwithin said envelope between said anode surfaces to maintain them at thesame operating potential, a control electrode comprising a pair of fiatplates electrically connected together within said envelope and disposedone on each side of said cathode, said control electrode having itssurfaces extending throughout the length of the emissive surface of saidcathode in planessubstantially at right angles to said anode surfaces, amagnet providing a magnetic field acting in a direction substantially atright angles to the axis of said cathode and said anode surfaces, saidmagnetic field having a strength with relation to the spacing of saidcontrol electrodes to permit a, relatively high positive potential to beapplied to said control electrodes without having significant electroncurrent flow to said control electrodes, said control electrodes andanodes being made of a readily degassed but non-magnetic material toavoid weakening or distortion of the magnetic field acting upon theelectrons emitted from the cathode.

JAMES H. BURNETT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,132,946 Fritz Oct. 11, 19382,177,065 Hollmann Oct. 24, 1939 2,187,171 Okabe Jan. 16, 1940 2,227,078Gerhard Dec. 31, 1940 2,248,712 Litton July 8, 1941 2,259,549 BradenOct. 21, 1941

